1. Field of the Invention
This invention relates to a pneumatically driven power tool, more particularly to a cage device for a rotary impact mechanism of a pneumatically driven power tool.
2. Description of the Related Art
Referring to FIG. 1, a conventional rotary impact mechanism 1 is shown to include a hollow cage member 11, two hammer members 12, two pins 13, and a power output shaft 14.
The cage member 11 is coaxially mounted around the output shaft 14, and is rotatable with respect to the output shaft 14. The cage member 11 includes a pair of longitudinally spaced end plates 111 joined by a pair of diametrically spaced connecting portions 112 so as to form a space 113 therein. The pins 13 are inserted fixedly into two elongate slots 114 formed in the connecting portions 112 and extending through the end plates 111. An air motor 17 has a drive output shaft 171 engaging an engaging hole 116 of the rear end plate 111. The power output shaft 14 is inserted into the space 113 via an inserting hole 115 of the front end plate 111, and has an impact receiving anvil jaw with two impact receiving surfaces 141.
The hammer members 12 are disposed to surround the power output shaft 14. Each hammer member 12 includes an inner annular wall 123 with two impact jaws 124 to intermittently engage and disengage the impact receiving surfaces 141, and an outer annular wall which has a groove 121 and a limiting notch 122 respectively engaging with the pins 13 such that each hammer member 12 is pivotable relative to one of the pins 13, thereby bringing the impact jaws 124 to exert an instant impact on the impact receiving surfaces 141.
The conventional cage member 11 is generally made from a metal block to form the end plates 111 and the connecting portions 112, and the elongate slots 114 need to be machined longitudinally therein in a precise manner, thereby resulting in inconvenience during the manufacture of the cage member 11.